Fix timeout_scale= call to use the correct receiver

* See ruby/test-unit-ruby-core#23

Author: eregon

tool/lib/envutil.rb

@@ -48,14 +48,6 @@ class << self
     attr_reader :original_internal_encoding, :original_external_encoding,
                 :original_verbose, :original_warning
 
-    if RUBY_ENGINE == "truffleruby"
-      # Tests relying on timeout have high variance on TruffleRuby due to the highly-optimizing JIT, deoptimization, profiling interpreter, different GC, etc.
-      # Setting a default timeout scale helps avoid transient failures for tests relying on timeouts.
-      # We choose 10 because it is the same number used in CRuby CI on macOS:
-      # https://github.com/ruby/ruby/blob/9d46b0c735877f152a0b4b16b8153c6f395dee28/.github/workflows/macos.yml#L133
-      self.timeout_scale = 10
-    end
-
     def capture_global_values
       @original_internal_encoding = Encoding.default_internal
       @original_external_encoding = Encoding.default_external
@@ -71,6 +63,14 @@ def capture_global_values
     end
   end
 
+  if RUBY_ENGINE == "truffleruby"
+    # Tests relying on timeout have high variance on TruffleRuby due to the highly-optimizing JIT, deoptimization, profiling interpreter, different GC, etc.
+    # Setting a default timeout scale helps avoid transient failures for tests relying on timeouts.
+    # We choose 10 because it is the same number used in CRuby CI on macOS:
+    # https://github.com/ruby/ruby/blob/9d46b0c735877f152a0b4b16b8153c6f395dee28/.github/workflows/macos.yml#L133
+    self.timeout_scale = 10
+  end
+
   def apply_timeout_scale(t)
     if scale = EnvUtil.timeout_scale
       t * scale